<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>深度监视</title>
    <!-- 引入vue -->
    <script type="text/javascript" src="../js/vue.js"></script>
</head>

<body>
    <div id="root">
        <h3>今天天气{{state}}</h3>
        <button @click="changeWeather">切换天气</button>
    </div>
    <script>
        Vue.config.productionTip = false // 以阻止 vue 在启动时生成生产提示。

        const vm = new Vue({
            el: "#root",
            data: {
                isHot: true,
            },
            computed: {
                state() {
                    return this.isHot ? '炎热' : '凉爽'
                }
            },
            methods: {
                changeWeather() {
                    this.isHot = !this.isHot
                }
            },
            watch: {
                // 正常写法
                /*isHot: {
                    immediate: true, // 初始化时让handler调用一下
                    deep: true, // 深度监视
                    handler(newValue, oldValue) {
                        console.log('isHot被修改了');
                    }
                },*/
                // 简写
                isHot(newValue, oldValue) {
                    console.log('isHot被修改了');
                }

            }
        })
    </script>
</body>

</html>